1. Field of the Invention
This invention relates generally to improvements in surgical instruments, and more particularly, but not by way of limitation, for surgical instruments employing radio frequency electrical energy in electrodesiccation, fulguration and biactive or bipolar coagulation.
2. Description of the Prior Art
The prior art comprises a number of teachings of radio frequency electrosurgical apparatus. One of the more significant developments in the field of electrosurgical apparatus is the development by the Medical Division of the Birtcher Corporation, Los Angeles, Calif., of the electrosurgical device known as the Birtcher HYFRECATOR .RTM.. This device has received extensive acceptance by the medical community since its introduction in 1937.
A distinct disadvantage of the Birtcher HYFRECATOR .RTM. and those other devices similar thereto, is the reliance upon foot-operated switches to activate and deactivate the signal generator during the operation of the instrument by the physician. It is deemed most advantageous to provide means for activating and deactivating the signal generator directly from the electrode assembly connected thereto. The fact that radio frequency energy is conducted directly to the electrode in the electrode assembly presents a distinct problem in designing an effective switching mechanism controlled from the electrode assembly due to the radio frequency interference induced in the switching circuitry by the radio frequency signal in the electrode.
U.S. Pat. No. 3,100,489, to R. W. Bagley, discloses a form of switching device which utilizes extensive radio frequency filtering comprising radio frequency choke coils and radio frequency filter capacitors to interconnect a switching circuit with the radio frequency operating circuit of the cautery device. This apparatus further relies on a double pole single throw electromechanical relay to effect the switching of the power circuit to the signal generator. Such a mechanism is bulky, expensive and relatively unreliable owing to the fact that the radio frequency signal is electrically connected through a filter network directly to the circuit connected to the relay. The sheer size of such a device makes it undesirable and inappropriate for use with the smaller electrosurgical devices such as the Birtcher HYFRECATOR .RTM. and the like.